(a) Field of the Invention
The present invention relates to a power supply apparatus and a driving method thereof.
(b) Description of the Related Art
A power supply apparatus is an apparatus that converts a predetermined input voltage to a desired output voltage. Such a power supply apparatus is installed in various electronic device products to convert an external AC voltage to various voltages required for driving of the electronic device products.
As a means for replacing existing lighting devices such as a fluorescent lamp and an incandescent lamp, a light emitting LED has been spotlighted. The light emitting LED has a semipermanent characteristic and power consumption of the LED is low so that the light emitting LED can be variously used. As an apparatus for supplying a predetermine current to such a light emitting LED, a power supply apparatus is mounted. The power supply apparatus receives external AC power and provides a predetermined current for driving the LED.
Meanwhile, a power supply apparatus for the light emitting LED has a dimmer and thus a user can control brightness of the LED. As an example of the dimmer, a triac dimmer may be used, and the triac dimmer controls an angle size of a waveform of an externally input AC voltage by user's control. In addition, the angle size of the voltage waveforms output from the triac dimmer is sensed and a reference voltage (or, current) is changed according to the sensed angle size such that an output current is controlled. Here, the reference voltage (or, current) is a voltage used to control a duty of a main switch, and the reference voltage is compared with a voltage that corresponds to the output current of the power supply apparatus. That is, the reference voltage is changed by user's control in the conventional power supply apparatus for an LED, and the output current is changed according to the change of the reference voltage such that brightness of the LED is controlled.
Such a conventional LED power supply apparatus additionally needs a sense circuit to sense an angle size with respect to an output waveform of a triac dimmer, and accordingly a circuit for converting a reference voltage (or, current) according to the angle sensed by the sense circuit is additionally required.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.